(a) Field of the Invention
The present invention relates to a system and a method for controlling an emergency driving for a fuel cell vehicle.
(b) Description of the Related Art
Generally, a fuel cell vehicle uses a fuel cell as a main power supply and a supercapacitor as an auxiliary power supply. The fuel cell vehicle configured to use a braking resistor to prevent an overvoltage of the typical supercapacitor has used a control method for detecting and cutting off the occurrence of a short-circuit of a semiconductor device (IGBT) of a chopper which is an electrical contact apparatus of a braking resistor circuit.
FIG. 1 illustrates a power system of the typical fuel cell vehicle according to the related art. Referring to FIG. 1, a power system 10 of the typical fuel cell vehicle includes a supercapacitor 14 charged with a voltage generated from a fuel cell 11 and a driving motor 13 during regenerative braking, a chopper 15 configured to prevent an overvoltage of the supercapacitor 14, and a braking resistor 16.
The power system 10 is configured to turn on a supercapacitor cutoff relay 17 when a chopper short-circuit error code is not present in a chopper controller flash memory during the starting of the fuel cell vehicle. When being driven in an initial charging mode of the supercapacitor 14, the power system 10 is configured to turn on an initial charging relay 18 after the fuel cell 11 generates a voltage to initially charge the supercapacitor 14 through the braking resistor 16.
Further, the power system 10 is configured to turn on a supercapacitor connecting relay 19 to connect the supercapacitor 14 to a main circuit when a difference between the voltage of the fuel cell 11 and the voltage of the supercapacitor 14 is reduced to a predetermined level due to the initial charging of the supercapacitor 14. The power system 10 for the fuel cell using the regenerative braking as the auxiliary braking means may consume electrical energy as thermal energy and reduce a voltage using the braking resistor 16 and the chopper 15 to prevent the voltage of the supercapacitor 14 from excessively increasing due to the substantial amount of regenerative braking during a deceleration in a high load.
However, in the typical power system 10, a deceleration of a downhill is sustained and thus, the voltage of the supercapacitor 14 may approach a threshold voltage or a substantial current may flow in the braking resistor through the chopper 15 by the regenerating braking energy. In particularly, the supercapacitor connecting relay 19 is turned off during the short-circuit of the chopper 15 to separate the supercapacitor 14 which is the auxiliary power supply from the main circuit. Voltages of high voltage terminal capacitors of various power parts suddenly increase during this process, causing potential damage due to a voltage exceeding a withstanding voltage limitation of a power device.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.